1. Field of the Invention
This invention relates to a robot apparatus performing jumping and a method for controlling the jumping of the robot apparatus.
2. Description of Related Art
Recently, a proposal has been made for a robot apparatus simulating the shape of an animal, or a so-called pet robot. This robot apparatus has the shape like that of a dog or a cat kept in a household at large, and behaves autonomously responsive to actions from a user (keeper) such as xe2x80x9cstrikingxe2x80x9d or xe2x80x9ccaressingxe2x80x9d or to surrounding environment. The autonomous behavior may be enumerated by, for example, xe2x80x9cbarkingxe2x80x9d or xe2x80x9clying downxe2x80x9d, as in the case of actual animals.
If the robot apparatus can behave more like actual animals, the apparatus can be felt to resemble actual living animals more closely, such that the user (keeper) feels more akin to and satisfied with the robot apparatus. This also enhances amusement properties of the robot apparatus.
For example, if a robot apparatus can jump as actual living animals, the keeper feels more akin to and satisfied with the robot apparatus.
Meanwhile, a number of researches and developments have been conducted on dynamic running movements of a quadruped robot apparatus. For example, towards the middle of eighties, Raibert developed a robot apparatus, inclusive of a quadruped robot, performing a series of jumping ands running movements. This quadruped robot could perform running in four running styles, namely trotting, which is running at a rapid speed, pacing, which is running at a constant speed, pronking, which is jumping with all of four legs, approximately simultaneously, and bounding, which is jumping as front and back legs alternately touch the ground. Raibert also proposed running control, comprised of three elements, which control can be applied in substantially the same manner to one-legged, two-legged and quadruped robots,
More recently, Buehler et al., attempted to improve the three-element algorithm and realized a stable bounding for quadruped robots by taking advantage of torque control at a stance position and quasi-static slip control algorithm.
Moreover, Talebi and Buehler showed that a simplified control rule can be exploited in order to stabilize the running despite the fact that task-level feedback, such as feedback on the level of advancing speed or trunk angle, is not used, and further expanded this operation. By this approach, more efficient and powerful running could be achieved.
In addition, Akiyama and Kimura et al., realized planar running using a biologically disclosed motor control model.
The results of the above-mentioned researches are shown for example in the following publications:
[1] M. H. Raibert, xe2x80x9cLegged Robot That Balancexe2x80x9d, MIT Press. Cambridge, Mass., 1986;
[2] M. H. Raibert, 1990 Trotting, Pacing, and Bounding by a Quadruped Robot, J. Biomechamics, Vol.23, Suppl. 1, 79-98;
[3] D. Papadopoulos and M. Buehler, xe2x80x9cStable Running in a Quadruped Robot with Compliant Legsxe2x80x9d, IEEEInt. Conf. Robotics and Automation, San Francisco, Calif., April 2000;
[4] S. Talebi, I. Poulakakis, E. Papadopoulos and M. Buehler, xe2x80x9cQuadruped Robot Running with a Bounding Gaitxe2x80x9d, Int. Symp. Experimental Robotics, Honolulu, Hi., Dec. 2000;
[5] S. Akiyama and H. Kimura, xe2x80x9cDynamic Quadruped Walk Using Neural Oscillators-Realization of Pace and Trotxe2x80x9d 23th Annual Conf. RSJ, p.227 to 228, 1995.
Among the results of past searches in a robot apparatus, performing stabilized jumping, that by MIT Legged Laboratory is most well-known. This technique uses a highly simplified control rule, which is thought to represent effective means in application to a robot apparatus, for which cost is of primary consideration, such as an entertainment robot, e.g., a pet robot.
However, this technique is premised on the use of a pneumatically driven translatory joint, performing stretching/contracting movements, at the legs, and hence is difficult to apply to a robot apparatus having a leg structure simulating an animal, such as a pet robot walking on four legs. That is, such pet robot has joints driven by an actuator, with its leg structure simulating that of an animal, so that the above-mentioned pneumatically driven translatory joint cannot be used, thus raising difficulties in performing stabilized jumping movements.
That is, in a robot apparatus having a leg structure simulating that of an animal, walking on four legs, it has not been possible to realize a low-cost mechanism of high reliability which enables jumping movements.
It is therefore an object of the present invention to provide a robot apparatus enabling jumping movements and a jumping controlling method for this robot apparatus.
In one aspect, the present invention provides a robot apparatus in which a leg part including a link mechanism connected to an elastic member is rotationally mounted to a trunk part through driving means, wherein the elastic member is mounted so that a substantially linear relation will be maintained between the distance between the driving means and the distal end of the leg part and a force virtually operating between the driving means and the distal end of the leg part.
The link mechanism includes a first connecting bar having its one end rotationally connected to a rotational member rotated by the driving means and having its other end rotationally connected to a connecting member, and a second connecting bar having its one end rotationally connected to the rotational member and having its other end rotationally connected to the connecting member, to form a four-point link mechanism, which four-point link mechanism is formed to provide for a linear trajectory of the distal end of the leg part.
With this leg part of the robot apparatus, the distance between the driving means and the distal end of the leg part has a substantially linear relation with respect to a force virtually operating between the driving means and the distal end of the leg part. In another aspect, the present invention provides a robot apparatus having at least one pair of leg parts provided protruding from a main body portion, in which at least one pair of the leg parts may transfer from a stance state with the distal ends of the leg parts touching the ground to a flight state with the distal ends floating in air after lapse of a preset time, by way of performing jumping.
The robot apparatus includes a pair of front leg parts and a air of back leg parts, wherein at least one of the front and back leg parts may transfer from a stance state with the distal ends of the leg parts touching the ground to a flight state with the distal ends floating in air after lapse of a preset time.
With the robot apparatus, the jumping mode can be switched by changing the touchdown angle and the delay time of at least one leg part. The jumping mode may at least include a pronking mode of jumping with both the front and back legs touching the ground and jumping substantially simultaneously and abounding mode of jumping with the front and back leg parts alternately touching the ground.
With this robot apparatus, at least one of the leg parts may transfer from the stance state, in which the distal end of the leg part touches the ground, to a flight state in which the distal end of the leg part is floated in air, after lapse of a preset time, to perform jumping. The jumping mode can be switched by varying the touch angle of the leg and the delay time.
In still another aspect, the present invention provides a method for controlling the jumping of a robot apparatus in which a leg part including a link mechanism connected to an elastic member is rotationally mounted to a trunk pat through driving means, wherein the elastic member is mounted so that a substantially linear relation will be maintained between the distance between the driving means and the distal end of the leg part and a force virtually operating between the driving means and the distal end of the leg part.
The link mechanism may include a first connecting bar having its one end rotationally connected to a rotational member rotated by the driving means and having its other end rotationally connected to a connecting members and a second connecting bar having its one end rotationally connected to the rotational member and having its other end rotationally connected to the connecting member, to form a four-point link mechanism, which four-point link mechanism is formed to provide for a linear trajectory of the distal end of the leg part.
With this jump controlling method for the robot apparatus, a substantially linear relation may be maintained between the distance between the driving means and the distal end of the leg part and a force virtually operating between the driving means and the distal end of the leg part.
In yet another aspect, the present invention provides a method for controlling the jumping of a robot apparatus having at least one pair of leg parts protruding from a main body portion, in which the method includes a delaying step for providing a delay of a preset time from the stance state with the at least one pair of leg parts touching the ground and a step of transferring to a flight state with the at least one pair of legs floating in air after lapse of the delay time. The transferring step is made sequentially from the stance state through the delaying step to the flight state to perform jumping.
The robot apparatus may include a pair of front leg parts and a pair of back leg parts. At least one of the front leg parts and the back leg parts is subjected to delay of a preset time in the delay step.
The touchdown angle and the delay time of the at least one leg part may be changed to switch the jumping mode, The jumping mode may at least include a pronking mode of jumping with both the front and back legs touching the ground and jumping substantially simultaneously and a bounding mode of jumping with the front and back leg parts alternately touching the ground.
With this method for controlling the jumping of a robot apparatus, at least one pair of the leg parts may transfer from the stance state in which the distal ends of the leg parts touch the ground to a flight state in which the distal ends of the leg parts float in air, after lapse of a preset time, to perform jumping. Moreover, the jumping mode can be switched by changing the touchdown angle of the leg part and the delay angle.